1. Field of the Invention
The present invention relates to a post-injection needle sheath for a hypodermic syringe needle and more, particularly to a post-injection needle sheath for a hypodermic syringe needle which is easily and conveniently actuated, is self-sealing and simultaneously renders the syringe needle inoperable.
2. Description of the Prior Art
For many years, health care workers, including doctors, nurses, physicians, laboratory personnel and housekeeping personnel of hospitals, doctor's offices and the like were prone to injuries from accidental sticking of the needle into the worker's skin, especially after removal of a needle from a body of a patient and during subsequent disposal of the needle. Such injuries pose grave dangers, particularly if the patient has been exposed to hepatitis and other communicable diseases which can be transmitted by body fluids. The health hazards associated with such injuries became even greater in view of the acquired immune deficiency syndrome (AIDS).
Numerous attempts, including needle protectors, have therefore been made to sheath a syringe needle after its use and to provide for its safe disposal. Needle protectors are generally well known and abound. One such needle protector is disclosed in U.S. Pat. No. 5,015,242. This patent discloses a needle sheath made of a resilient material and having an accordion or bellows shape. The sheath is attached at one of its end to the needle hub. In the "use" position, the needle sheath is compressed and held in its compressed position by an L-shaped bendable retaining element which is also secured to the needle hub. Upon withdrawal of the needle from the body of a patent, the retaining element is bent away, and the sheath expands covering the needle. This construction of a sheath however has numerous drawbacks. It is highly desirable that the protector be actuated with the same hand that holds the syringe, when the needle is withdrawn from the body of a patient, as the other hand is generally used to apply alcohol or other disinfectant to a patient's body. However, it would be difficult to bend away the retaining member with a finger of the same hand used to apply the injection. The finger would have to be inserted between the retaining member and the sheath adjacent to the short leg of the L-shaped retaining member and then, a substantial force must be applied by the finger to bend the retaining member away. Further, even after the sheath covers the needle, nothing prevents the sheath from accidental compression and thus exposure of the needle.
Another type of a post-injection needle sheath is disclosed in U.S. Pat. No. 4,804,371. U.S. Pat. No. 4,804,371 likewise discloses an accordion - or bellows-shaped needle sheath retained in a compressed position during use of the needle. The sheath expands to cover the needle after the needle is withdrawn. This sheath, as the sheath of U.S. Pat. No. 5,015,242, can also be accidentally compressed, exposing the needle.
Yet another post-injection sheath is disclosed in German Offenlegungsschrift DE 38 08 688. The German document discloses a protective cover for a syringe needle, including a resilient sheath attached at one of its ends to the needle hub, with an end cup-shaped member secured to the other end of the sheath. This member has an opening through which the needle extends with the opening being defined by a central tubular portion formed integrally with the end surface of the cup-shaped member. During needle use, the cup-shaped member compresses the sheath and is secured (clamped) to the needle hub. Upon withdrawal of the needle from a stick in the body of a patient, the sheath expands covering the needle. At that point, eccentric or side forces acting on the cup-shaped member displace it relative to the needle axis so that the needle end is located in the space between the circumferential surface of the cup-shaped member and its central tubular portion. To this end, the central tubular portion is formed with an eccentricity relative to the needle axis. However, because the eccentricity is very small (0.2-0.5 mm), the needle would not extend into the guide passage, especially if the production tolerances are taken into account.